void MainWindow::DrawChessAtPoint(QPainter& painter,QPoint& pt)
{
	//painter.drawRect( (pt.x()+0.5)*RECT_WIDTH,(pt.y()+0.5)*RECT_HEIGHT,RECT_WIDTH,RECT_HEIGHT);

	QPoint ptCenter((pt.x()+0.5)*RECT_WIDTH,(pt.y()+0.5)*RECT_HEIGHT);
	painter.drawEllipse(ptCenter,RECT_WIDTH / 2,RECT_HEIGHT / 2);
}